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Old 25th February 2021, 12:56 AM   #107
Skeptic Ginger
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Originally Posted by Sherkeu View Post
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I'm not sure why we do not include humans as intermediary hosts on the path- the path back to humans. We do know now we can pass it to cats, dogs, and cattle. Maybe more. Probably more. And then the process could reverse. There is a team of researchers looking into that now.

We need a virologist in here.
Not a virologist but I do have expertise in this subject from what I know about influenza species jumps. It's a matter of how close our cells are (respiratory and GI tracks) to the species harboring the pathogen.

These viruses have a particular affinity to certain cells. They can enter the cell easily because of the surface proteins and efficiently reproduce once in the cell.

So for example a bird flu might be adapted to the respiratory cells in a pig but not as close to the human cells it needs to efficiently reproduce in. But as it infects the pig cells it adapts with the result being a closer match to the human cells. That was just an example but we can be infected by both bird and pig flu strains but humans don't typically get infected by equine influenza strains for example.

The H5N1 influenza can infect humans when they have close contact with infected birds. And if that happens one too many times the strain could adapt to human cells in the respiratory track and become a pandemic flu. The molecular structure needed to adapt is thought to be similar to the changes the 1918 flu strain had. By comparing the two and knowledge about which parts of the genome are the parts involved in adapting, it was clear very few mutations could result in the next 1918-like flu event.

CIDRAP: Scientists recreate 1918 flu virus, see parallels with H5N1 Scary stuff.

So it doesn't always have to be an intermediary species involved in the jump.

Last edited by Skeptic Ginger; 25th February 2021 at 12:58 AM.
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